Silicone-acrylate impact modifier

ABSTRACT

A silicone-acrylate impact modifier composition, wherein said impact modifier composition comprises structural units derived from:  
     at least one silicone rubber monomer,  
     a branched acrylate rubber monomer having the formula:  
                 
 
     wherein R 1  is selected from hydrogen and C 1 -C 8  linear and branched hydrocarbyl groups; and R 2  is a branched C 3 -C 16  hydrocarbyl group;  
     a first graft link monomer,  
     a polymerizable alkenyl-containing organic material, and  
     and a second graft link monomer.  
     The silicone-acrylate impact modifier compositions disclosed herein are useful for making molding compositions, which are useful for producing various articles, especially for outdoor applications.

BACKGROUND

[0001] The disclosure relates generally to silicone-acrylate rubbercompositions and their use as impact modifiers in resin moldingcompositions, particularly those comprising thermoplastic resins.Furthermore, the disclosure also relates to an emulsion polymerizationmethod for making the silicone-acrylate impact modifiers. As usedhereinafter, the expressions “silicone-acrylate rubber” and“silicone-acrylate rubber graft hybrid” mean an interpenetratingcomposite of silicone rubber and polyacrylate rubber, where the siliconerubber and polyacrylate rubber are entangled in an inseparable fashionat the molecular level.

[0002] Butadiene-based impact modifiers, such asacrylonitrile-butadiene-styrene (also called ABS) copolymers and methylmethacrylate-butadiene-styrene (also called MBS) copolymers have beenpreviously used to improve the impact performance of thermoplasticmaterials. However, due to the presence of unsaturation, thesebutadiene-based copolymers respond poorly to weathering. Weathering is aphenomenon where the combined effect of several natural elements,particularly oxygen in air and sunlight act upon the polymer therebycausing the material to degrade. Generally, this degradation isobservable by a yellowing and loss of surface gloss of the polymermaterial. Impact modifiers based on acrylonitrile-styrene-acrylate (alsocalled ASA) copolymers avoid the issues faced by the butadiene-basedpolymers, however, these materials only have room temperature ductility.Acrylate rubbers are widely used for impact modification ofthermoplastic materials where weathering is a concern. However, theimpact strength of acrylate rubber-modified thermoplastic materials atlow temperatures, such as 0° C., or below are substantially reduced, ascompared to thermoplastic materials containing other organic blends,such as the butadiene-based polymers. Efforts have been made to usesilicone-based materials to improve low temperature impact. For example,silicone-polycarbonate copolymers show good ductility at −40° C., butthey can be used only in polycarbonates and polycarbonate blends.Efforts to improve the low temperature impact of thermoplastic polymercompositions by using silicone rubber-based impact modifiers, such asMitsubishi Rayon's S 2001 are known. However, the low temperature impactand ductility performance, as measured for example, by theductile-to-brittle transition temperature (hereinafter referred to as“DBTT”) is in some cases not up to the desired mark. Therefore, there isa continued need for impact modifiers that can afford superior impactproperties, lower ductile-to-brittle transition temperatures(hereinafter sometimes referred to as DBTT's), and outstandingweatherability performance, that is, slow down or prevent yellowing andloss of surface gloss, in polymer compositions and articles comprisingthese polymer compositions. Such impact modifiers, when incorporatedinto polymer resin systems are expected to find a wide variety ofapplications, especially outdoor applications.

BRIEF DESCRIPTION

[0003] Briefly, one embodiment of the disclosure is a silicone-acrylateimpact modifier composition, where the impact modifier compositioncomprises structural units derived from: at least one silicone rubbermonomer, a branched acrylate rubber monomer having the formula:

[0004] where R¹ is selected from hydrogen and C₁-C₈ linear and branchedhydrocarbyl groups; and R² is a branched C₃-C₁₆ hydrocarbyl group; afirst graft link monomer, a polymerizable alkenyl-containing organicmaterial, and a second graft link monomer.

[0005] Another embodiment of the disclosure is a silicone-acrylateimpact modifier composition, where the impact modifier compositioncomprises structural units derived from: a silicone rubber monomercomprising octamethylcyclotetrasiloxane and tetraethoxysilane; abranched acrylate rubber monomer selected from the group consisting ofiso-octyl acrylate, 6-methyloctyl, 7-methyloctyl, and combinations ofthe foregoing branched acrylate rubber monomers; at least one firstgraft link monomer selected from the group consisting of(gamma-methacryloxypropyl)(dimethoxy)methylsilane and(3-mercaptopropyl)trimethoxysilane; a polymerizable alkenyl-containingorganic material comprising at least one of styrene,alpha-methylstyrene, acrylonitrile, methacrylonitrile, methylmethacrylate; and at least one second graft link monomer selected fromthe group consisting of allyl methacrylate, triallyl cyanurate, andtriallyl is isocyanurate.

[0006] Another embodiment of the disclosure is a molding compositioncomprising a polymer resin and a silicone-acrylate impact modifiercomposition, wherein said impact modifier composition comprisesstructural units derived from: at least one silicone rubber monomer, abranched acrylate rubber monomer having the formula:

[0007] wherein R¹ is selected from hydrogen and C₁-C₈ linear andbranched hydrocarbyl groups; and R² is a branched C₃-C₁₆ hydrocarbylgroup; a first graft link monomer, a polymerizable alkenyl-containingorganic material, and a second graft link monomer; wherein said moldingcomposition has a ductile-to-brittle transition temperature from about0° C. to about −60° C.

[0008] Another embodiment of the disclosure is a molding compositioncomprising a polymer resin and a silicone-acrylate impact modifiercomposition, wherein the silicone-acrylate impact modifier compositioncomprises structural units derived from: a silicone rubber monomercomprising octamethylcyclotetrasiloxane and tetraethoxysilane; abranched acrylate rubber monomer selected from the group consisting ofiso-octyl acrylate, 6-methyloctyl, 7-methyloctyl, and combinations ofthe foregoing branched acrylate rubber monomers; at least one firstgraft link monomer selected from the group consisting of(gamma-methacryloxypropyl)(dimethoxy)methylsilane and(3-mercaptopropyl)trimethoxysilane; a polymerizable alkenyl-containingorganic material comprising at least one of styrene,alpha-methylstyrene, acrylonitrile, methacrylonitrile, methylmethacrylate; and at least one second graft link monomer selected fromthe group consisting of allyl methacrylate and triallyl cyanurate;wherein said molding composition has a ductile-to-brittle transitiontemperature of less than or equal to about −60° C.

[0009] Another embodiment of the disclosure is a method for making asilicone-acrylate impact modifier composition, where the methodcomprises: emulsion polymerizing at least one silicone rubber monomerand a first graft link monomer at a temperature from about 30° C. toabout 110° C. to form a silicone rubber latex; adding to said siliconerubber latex, at a pH of about 4 to about 9.5, and a temperature ofabout 20° C. to about 90° C., at least one branched acrylate rubbermonomer to provide a latex comprising an emulsion polymerizedsilicone-acrylate rubber hybrid; grafting said silicone-acrylate rubberhybrid with a polymerizable alkenyl containing organic material and asecond graft link monomer to form a graft silicone-acrylate rubberhybrid latex; and coagulating, washing, and drying said graftsilicone-acrylate rubber hybrid latex to provide said silicone rubberimpact modifier composition; wherein said at least one branched acrylaterubber monomer has the formula:

[0010] wherein R¹ is selected from H and C₁-C₈ linear and branchedhydrocarbyl groups; and R² is a branched C₃-C₁₆ hydrocarbyl group.

DETAILED DESCRIPTION

[0011] The impact modified compositions disclosed herein display many ofthe properties that makes them valuable materials for use in outdoorapplications, especially in cold climates. The impact modifiercompositions display ductile-to-brittle transition temperatures(hereinafter sometimes referred to as “DBTT”) lower than or equal toabout −40° C., outstanding low temperature ductility and impact, andexcellent weatherability performance, while retaining the otherdesirable properties, such as heat distortion temperature (hereinaftersometimes referred to as “HDT”), tensile and flexural modulus, and meltvolume ratio (hereinafter sometimes referred to as “MVR”).

[0012] Suitable branched acrylates useful for the silicone-acrylateimpact modifier compositions of the disclosure are represented byformula (I):

[0013] where R¹ is selected from hydrogen and C₁-C₈ linear and branchedhydrocarbyl groups; and R² is a branched C₃-C₁₆ hydrocarbyl group. In anembodiment, the branched acrylate is one where R¹ is hydrogen and R² isat least one branched hydrocarbyl radical selected from 4-methylpentyl,4-methylhexyl, and 5-methylhexyl. In general the branched acrylates offormula (I) have structures in which the R² group is separated from theacrylate acyl oxygen (that is, the oxygen atom located next to theacrylate carbonyl group) by at least 2 CH₂ groups. In a particularembodiment, the branched acrylate is 6-methylheptyl acrylate. Thebranched acrylates can be prepared by methods known in the art. Forexample, reaction of acryloyl chloride with the appropriate branchedalcohol in the presence of a tertiary amine scavenger to trap thehydrogen chloride by-product furnishes the desired branched acrylateester. Some of the branched acrylates, such as 6-methylheptyl acrylateare commercially available from vendors, such as Aldrich ChemicalCompany. In another embodiment, the silicone-acrylate impact modifiercomposition further comprises structural units derived from at least oneacrylate monomer selected from the group consisting of methyl acrylate,ethyl acrylate, n-propyl acrylate, n-butyl acrylate.

[0014] The silicone-acrylate impact modifier comprises structural unitsderived from silicone rubber monomers. A variety of silicone rubbermonomers can be used. In general, the silicone rubber monomer comprisesat least one of a cyclic siloxane, tetraalkoxysilane, trialkoxysilane,(acryloxy)alkoxysilane, (mercaptoalkyl)alkoxysilane, vinylalkoxysilane,and allylalkoxysilane.

[0015] The silicone rubber monomer comprises at least one of a cyclicsiloxane of the formula (II):

[0016] where R³ and R⁴ are independently selected from hydrogen andC₁-C₁₀ alkyl and aryl radicals; and “n” is an integer having a valuefrom about 3 to about 20. In some embodiments, R³ or R⁴, or both can bearyl groups. Suitable non-limiting examples of aryl radicals includephenyl, tolyl, xylyl, and the like. Phenyl radical is a preferred arylradical since the phenyl-substituted silicone rubber monomers arerelatively more readily available. Some of the preferred silicone rubbermonomers include cyclic siloxanes, such as octamethylcyclotetrasiloxane,as shown for example in the Encyclopedia of Polymer Science andEngineering, volume 15, 2nd Edition, pp. 205-308 (1989), John Wiley andSons. Other examples of cyclic siloxanes include without limitation,decamethylcyclopentasiloxane, dodecamethylcyclohexasiloxane,trimethyltriphenylcyclotrisiloxane,tetramethyltetraphenylcyclotetrasiloxane,tetramethyltetravinylcyclotetrasiloxane andoctaphenylcyclotetrasiloxane. These or similar cyclic siloxanes may beused alone or in combination.

[0017] The tetraalkoxysilane and trialkoxysilane type silicone rubbermonomers are represented by the general formula (III):

(R⁵)_(s)Si(OR⁶)_(4-s)   (III)

[0018] where R⁵ independently comprises hydrogen and C₁-C₁₀ alkyl andaryl radicals; R⁶ independently comprises C₁-C₄ hydrocarbyl radicals,and “s” is an integer having a value from about 0 to about 1. One ormore of the hydrocarbyl radicals in the tetraalkoxysilane can also bearyl radicals. Suitable non-limiting examples of aryl radicals includephenyl, tolyl, xylyl, and the like. Phenyl radical is a preferred arylradical since the phenyl-substituted silicone rubber monomers arerelatively more readily available. In an embodiment,(hydrocarbyl)trialkoxysilanes can also be as suitable silicone rubbermonomers. Examples of suitable tetraalkoxysilanes include, but are notintended to be limited to tetramethoxysilane, tetraethoxysilane,tetraisopropoxysilane, and tetrabutyloxysilane, and the like. Examplesof suitable (hydrocarbyl)trialkoxysilanes include, but are not intendedto be limited to methyltrimethoxysilane, methyltriethoxysilane,phenyltrimethoxysilane, phenyltriethoxysilane, and the like. In aparticular embodiment, tetraethoxysilane or tetraethylorthosilicate(hereinafter sometimes also referred to as “TEOS”) can be convenientlyused as a silicone rubber monomer. The tetraalkoxysilanes andtrialkoxysilanes can be used at from about 0.1% to about 30% by weightof the overall monomer mixture used for preparing the silicone-acrylateimpact modifier composition.

[0019] The first graft link monomer used for preparing the siliconerubber impact modifier composition comprises at least one of an(acryloxy)alkoxysilane, a (mercaptoalkyl)alkoxysilane, avinylalkoxysilane, and an allylalkoxysilane.

[0020] Suitable (acryloxyalkyl)silanes that can be used as the firstgraft link monomer are of the formula (IV):

[0021] where R⁷, R⁸, and R⁹ are independently selected from hydrogen andC₁-C₆ hydrocarbyl radicals; [A] is a C₁-C₁₂ alkylene radical; R¹⁰ isselected from hydrogen and C₁-C₁₀ hydrocarbyl radicals; R¹¹ is selectedfrom C₁-C₆ hydrocarbyl radicals; and “m” is integer having a value from0 to about 1. In an embodiment, R⁷and R⁸ are hydrogen, R⁹ is methyl, and[A] is a —CH₂CH₂CH₂— radical. In another embodiment,(gamma-methacryloxypropyl)silanes, in which R¹⁰ is a methyl or a phenylgroup; and R¹¹ is a methyl, ethyl, or an isopropyl group can be used inthe impact modifier compositions disclosed herein.(Gamma-methacryloxypropyl)dimethoxymethylsilane and(Gamma-methacryloxypropyl)trimethoxysilane are particularly convenientand versatile first graft link monomers due to their ready availability.The (acryloxy)silanes can be used at from about 0.1% to about 30% byweight of the overall monomer mixture used for preparing thesilicone-acrylate impact modifier composition.

[0022] Mercaptan-functionalized (hydrocarbyl)trialkoxysilanes areparticularly valuable silicone rubber monomers. Examples of suitablemercaptan-functionalized (hydrocarbyl)trialkoxysilanes include(3-mercaptopropyl)trimethoxysilane (hereinafter sometimes referred to as“MPTMS”), (4-mercaptobutyl)trimethoxysilane,(3-mercaptoethyl)trimethoxysilane, (3-mercaptopropyl)triethoxysilane,and the like.

[0023] Another type of possible silicone rubber monomer is a substitutedor an unsubstituted allylalkoxysilane of the formula (V):

[0024] where R¹², R¹³, and R¹⁴ are independently selected from hydrogenand C₁-C₄ hydrocarbyl radicals; R¹⁵ independently comprises C₁-C₈hydrocarbyl radicals, R¹⁶ independently comprises C₁-C₄ hydrocarbylradicals, and “t” is an integer having a value from 0 to about 1.Examples of suitable allylalkoxysilanes include, but are not intended tobe limited to allyltrimethoxysilane, allyltriethoxysilane,crotyltrimethoxysilane, crotyltriethoxysilane,(3-phenyl-2-propenyl)trimethoxysilane, and the like. In a particularembodiment allyltrimethoxysilane is a suitable silicone rubber monomer.In other embodiments, the silicone rubber monomer can also comprisecompounds that have 2 alkoxy groups and 2 allylic groups about thesilicon atom. Furthermore, the 2 alkoxy groups can be the same ordifferent. Likewise, the 2 allylic groups can be the same or different.The allylalkoxysilanes can be used at from about 0.1% to about 30% byweight of the overall monomer mixture used for preparing thesilicone-acrylate impact modifier composition.

[0025] Vinylalkoxysilanes can also be used as suitable first graft linkmonomers. Suitable vinylalkoxysilanes have the formula (VI):

[0026] where R¹⁷, R¹⁸, and R¹⁹ are independently selected from hydrogenand C₁-C₄ hydrocarbyl radicals; R²⁰ independently comprises C₁-C₈hydrocarbyl radicals, R²¹ independently comprises C₁-C₄ hydrocarbylradicals, and “u” is an integer having a value from 0 to about 1.Suitable vinylalkoxysilanes include vinyltrimethoxysilane,vinyltriethoxysilane, (1-propenyl)trimethoxysilane,styryltrimethoxysilane, divinyldimethoxysilane, divinyldiethoxysilane,and the like. The vinylalkoxysilanes can be used at from about 0.1% toabout 30% by weight of the overall monomer mixture used for preparingthe silicone-acrylate impact modifier composition.

[0027] In an embodiment, the first graft link monomer is at least oneselected from the group consisting of(gamma-methacryloxypropyl)(dimethoxy)methylsilane,(3-mercaptopropyl)trimethoxysilane, vinyltrimethoxysilane, andallyltrimethoxysilane. It will be apparent to those skilled in the artthat different combinations of the above-mentioned different types offirst graft link monomer can be used to form the silicone-acrylateimpact modifier composition.

[0028] The second graft link monomer is at least one polyethylenicallyunsaturated compound having at least one allyl group. In one embodiment,the polyethylenically unsaturated compound is at least one selected fromthe group consisting of allyl methacrylate, triallyl cyanurate(hereinafter sometimes referred to as “TAC”), triallyl isocyanurate, anddiallylmaleate.

[0029] The polymerizable alkenyl containing organic material comprisesat least one vinyl aromatic monomer, olefinic nitrile; and branched andunbranched acrylate monomers. Suitable alkenyl containing organicmaterials used for preparing the silicone rubber compositions includeswithout limitation: styrene, divinylbenzene, alpha-methylstyrene, vinyltoluene, halogenated styrene, and the like; methacrylates, such asmethyl methacrylate and 2-ethylhexyl methacrylate; linear acrylates suchas methyl acrylate, ethyl acrylate, n-propyl acrylate, n-butyl acrylate;n-pentyl acrylate, n-hexyl acrylate, n-heptyl acrylate, and n-octylacrylate; olefinic nitriles, such as acrylonitrile andmethacrylonitrile; olefins such as ethylene, propylene, butadiene,isoprene, and chloroprene; chloroprene, and 5-vinyl-2-norbornene, andother vinyl compounds such as acrylamides, N-(mono- or di-substitutedalkyl)acrylamides, vinylimidazole, vinyl acetate, vinyl alkyl ethers,vinyl chloride, vinyl furan, N-vinyl carbazole, vinyl pyridine, vinylpyrrolidines, vinyl acetate, vinyl chloride, vinyl alkyl ethers, allylmethacrylate, triallyl cyanurate, triallyl isocyanurate, ethylenedimethacrylate, diallyl maleate, maleic anhydride; maleimide compoundssuch as maleimide or N-phenyl (or alkyl) maleimide; and mixtures ofthese monomers. In an embodiment, the polymerizable alkenyl containingorganic material is at least one selected from the group consisting ofstyrene, alpha-methylstyrene, acrylonitrile, methacrylonitrile, butylacrylate, and (meth)acrylates, methyl methacrylate.

[0030] The silicone-acrylate impact modifier compositions disclosedherein can be prepared by emulsion polymerization techniques. In thefirst step of the technique, at least one silicone rubber monomer isreacted with at least one first graft link monomer at a temperature fromabout 30° C. to about 110° C., and preferably from about 75° C. to about95° C., to form a silicone rubber latex. An effective amount of asurfactant can be used initially in the reactor as part of the agitatedaqueous mixture, or it can be introduced with the silicone rubbermonomers. Surfactants that can be used include acidcatalyst-surfactants, for example, sulfonic acids, such as alkyl-, andalkaryl-arylsulfonic acids and mixtures of surface-active sulfonic acidsalts with strong mineral acids. Dodecylbenzenesulfonic acid is apreferred surfactant. In one embodiment of the method, the addition ofmonomers can be carried out batch wise or semi-continuously, and in adrop wise manner, over a period of up to 24 hours. The types of siliconerubber monomers and the first graft link monomers that can be used havebeen described previously. In another embodiment of the method,cyclooctamethyltetrasiloxane (hereinafter sometimes referred to as “D₄”)and tetraethoxyorthosilicate (sometimes also referred to as a siliconecross linking monomer) are reacted with(gamma-methaacryloxypropyl)methyldimethoxysilane (hereinafter sometimesreferred to as “MAPMDMS”) as a first graft link monomer to form siliconerubber particles. MAPDMMS facilitates chemical linking of acrylatechains onto the siloxane network. TEOS serves to form a weak cross-linkin the silicone rubber particles. The average size of the siliconerubber particle depends on the cross-linking density. A highercross-linking density generally results in a lowered particle size ofthe silicone rubber particles. In one embodiment, the method affordssilicone rubber having an average particle size from about 100nanometers to about 2 microns.

[0031] In the second step of the technique, at least one branchedacrylate rubber monomer of the structure (I) is polymerized with thesilicone rubber particles obtained in the first step to provide a latexcomprising an emulsion polymerized silicone-acrylate rubber hybrid. Inone embodiment, a branched acrylate rubber monomer of formula (I), suchas isooctyl acrylate is polymerized with the silicone rubber particlesin presence of a cross linking monomer, such as allylmethacrylate to getsilicone-acrylate hybrid latex particles. Allylmethacrylate performs thedual function of cross linking the acrylate chains as well as acting asa graft linker (via the allyl group) for the grafting reaction in thethird stage as described later in the disclosure. In another embodiment,a mixture of acrylate rubber monomers comprising the branched acrylaterubber monomers of structure (I) and linear acrylate rubber monomers,such as butyl acrylate can also be employed. The addition of theacrylate monomers to the silicone rubber latex occurs before, orconcurrently with addition of a polymerization catalyst. Thepolymerization catalyst can be any material known in the art to initiatefree radical polymerization, such as an alkali metal persulfate; ororganic soluble radical initiators, such as azobisisobutyronitrile, oran organic peroxide, such as benzoyl peroxide, dichlorobenzoyl peroxidecumene hydroperoxide, and tert-butyl perbenzoate, to polymerize thebranched acrylate rubber monomer and effect silicone-acrylate rubberhybrid formation. When an alkali metal persulfate catalyst is used, itis preferred that the persulfate be added over time to keep the vinylpolymerization running. This technique also minimizes degradation of thepersulfate under the acid conditions present during the polymerizationof the silicone rubber monomers. The emulsion polymerizedsilicone-acrylate rubber hybrid comprises about 95 parts to about 5parts by weight of silicone rubber, and about 5 parts to about 95 partsby weight of polyacrylate rubber, per 100 parts by weight of saidsilicone acrylate rubber hybrid.

[0032] In the third step, the latex comprising the emulsion polymerizedsilicone-acrylate rubber hybrid produced in the second step is reactedwith at least one polymerizable alkenyl containing organic material anda second graft link monomer to form a graft silicone-acrylate rubberhybrid latex. In an embodiment, the polymerizable alkenyl containingorganic material is polymerizable alkenyl containing organic material isat least one selected from the group consisting of styrene,alpha-methylstyrene, acrylonitrile, methacrylonitrile, and methylmethacrylate. The proportion of alkenyl organic containing material andthe silicone-acrylate rubber hybrid latex can vary widely, such as forexample, from about 0.15 part to about 3.0 part by weight of alkenylorganic containing material, per part of the silicone-acrylate rubberhybrid latex to form the graft silicone-acrylate rubber hybrid latex.When allyl methacrylate is used, in some situations, the residual allylgroups of allyl methacrylate resulting from the second step (describedabove) of the method itself acts as the second graft linker byfacilitating the grafting of polymerizable alkenyl containing organicmaterials, such as styrene and acrylonitrile monomers onto thesilicone-acrylate hybrid core. A variety of polymerizable alkenylcontaining organic materials, such as those disclosed previously can beemployed. When a mixture of styrene and acrylonitrile is used, thentheir weight ratio, in one embodiment, is between about 90:10 to about50:50.

[0033] The latex particles, of the graft silicone-acrylate rubber hybridare separated from the aqueous phase through coagulation (by treatmentwith a coagulant), and dried to a fine powder to produce thesilicone-acrylate rubber impact modifier composition.

[0034] The method described hereinabove can be generally used forproducing the silicone-acrylate impact modifier having a particle sizefrom about 100 nanometers to about 2 microns. In an embodiment, themethod described hereinabove can be carried out batch wise orsemi-continuously. In the batch wise process, all of the silicone rubbermonomers are charged into the polymerization reactor containing water,and the polymerization reaction is then carried out. In thesemi-continuous process, a portion of the mixture of the silicone rubbermonomers are taken in water in the polymerization reactor, andsubsequently the remaining portion of the silicone rubber monomermixture is added over a period of time to form the silicone rubber latexparticles. The semi-continuous process also includes the employment ofmild, and/or low shear non-homogenizing conditions during the emulsionpolymerization of the silicone rubber monomers.

[0035] The silicone rubber latex can also be synthesized through anemulsion polymerization route by using an additional homogenizationstep. The homogenization step generates particles having an average sizeof less than 500 nanometers with a substantially broad particle sizedistribution (hereinafter sometimes referred to as “PSD”). This createsperformance issues in polymer resin blends comprising, since specifictypes of polymer resin systems require a certain type of averageparticle size and PSD for the silicone-acrylate rubber impact modifiercompositions. For example, it is preferable to use silicone-acrylateimpact modifier compositions having a relatively smaller averageparticle size and narrower (that is, closer to a mono-modal) PSD forpolycarbonates, but a relatively broader (that is, closer to a bimodal)PSD for styrene-acrylonitrile copolymers. The method for forming thesilicone-acrylate impact modifier compositions disclosed herein includesin an embodiment, a semi-continuous emulsion polymerization processwithout the homogenization step, where the particle size can becontrolled such that one can achieve an average particle size of eitherless than or equal to about 500 nanometers, or greater than or equal toabout 500 nanometers.

[0036] The silicone-acrylate impact modifier compositions disclosedhereinabove are useful materials for preparing polymer moldingcompositions having improved properties, such as stiffness, lowtemperature ductility, weatherability, and chemical resistance. Theimpact modifier compositions also confer unexpectedly, a higher meltvolume rate to polymer and molding compositions during the processingstep. A higher melt volume rate generally translates to easierprocessing of the polymer or molding compositions, which can be asignificant benefit commercially.

[0037] The silicone-acrylate impact modifier can comprise from about 1part to about 50 parts by weight, in one embodiment, and from about 5parts to about 25 parts by weight, in another embodiment, per 100 partsby weight of the molding composition. More particularly, thesilicone-acrylate impact modifier comprises from 7 parts to about 15parts by weight, per 100 parts by weight of the molding composition.

[0038] The polymer comprising the polymer molding composition can be athermoset polymer, a thermoplastic polymer, or combinations of bothpolymers. In an embodiment, the thermoplastic polymer is selected fromthe group consisting of polycarbonates, polyesters, polyestercarbonates,polyamides, polyethersulfones, polyetherimides, polyphenylene ethers,acrylate polymers, styrenic polymers, vinyl halide polymers, and blendsof the foregoing polymers. Furthermore, the polymers comprising themolding compositions can be prepared by all methods known in the art.For example, suitable polycarbonates that can be used comprise thosethat are made by techniques, such as interfacial polymerization, meltpolycondensation, bischloroformate polymerization with dihydric phenolsand diols; and polymerization of dihydric phenols and diols withbissalicylate carbonates, such as bis(methylsalicylate)carbonate. Moreparticularly, the thermoplastic polymer is selected from the groupconsisting of bisphenol A polycarbonate,1,3-bis(4-hydroxyphenyl)-1-methyl-4-isopropylcyclohexane polycarbonate,polybutylene terephthalate, polyethylene terephthalate,acrylonitrile-styrene-acrylate core shell polymers,acrylonitrile-styrene-alpha-methylstyrene-acrylate core shell polymers,styrene-acrylonitrile copolymer, styrene-methacrylonitrile copolymer,acrylonitrile-butadiene-styrene copolymer,acrylonitrile-alpha-methylstyrene-butadiene copolymer, copolymerscomprising structural units derived from isophthalic acid, terephthalicacid, resorcinol, and bisphenol A (hereinafter sometimes referred to as“ITR”); and blends of the foregoing polymers. The ITR copolymers are aclass of polymers that have carbonate and ester functionalities on thepolymer backbone. They can be prepared by many generally knownpolymerization techniques known in the art. More particularly, the ITRcopolymers are prepared by a stepwise interfacial polymerizationprocess. A mixture of isophthaloyl chloride and terephthaloyl chlorideis added to an excess of resorcinol in a two-phase system comprisingaqueous alkali metal hydroxide and a halogenated hydrocarbon solvent,such as dichloromethane. The reaction is carried out in the presence ofan acid scavenger, such as triethylamine to trap the hydrogen chloridegenerated during the reaction, while maintaining the pH of the system atabout 7. The product of this reaction is an oligomeric polycarbonatehaving hydroxy group at both ends of the oligomer chain. In the nextstep, the oligomeric hydroxy-terminated polycarbonate is combined withan aromatic bisphenol, such as bisphenol A, and reacted with phosgene ina two phase system comprising aqueous alkali metal hydroxide arid ahalogenated hydrocarbon solvent, such as dichloromethane. A suitableacid scavenger, such as triethylamine is used to trap the hydrogenchloride by-product. A suitable amount of an appropriate monohydricphenol, such as phenol or para-cumylphenol is added as a chain stopperto cap the ends of the copolymer with phenyl or cumyl groups,respectively.

[0039] The polymer molding composition of the disclosure may alsocontain one or more antioxidants, heat stabilizers, ultraviolet(hereinafter referred to as “UV”) stabilizers, fire retardants, andcolorant compositions. The phenolic antioxidants useful in the instantcompositions embrace a large family of compounds, examples of which aregiven below. Non-limiting examples of antioxidants that can be used inthe molding composition of the disclosure includetris(2,4-di-tert-butylphenyl) phosphite,3,9-di(2,4-di-tert-butylphenoxy)-2,4,8,10-tetraoxa-3,9-diphosphaspiro[5.5]undecane,3,9-di(2,4-dicumylphenoxy)-2,4,8,10-tetraoxa-3,9-diphosphaspiro[5.5]undecane,tris(p-nonylphenyl) phosphite,2,2′,2″-nitrilo[triethyl-tris[3,3′,5,5′-tetra-tertbutyl-1,1′-biphenyl-2′-diyl]phosphite],3,9-distearyloxy-2,4,8,10-tetraoxa-3,9-diphosphaspiro[5.5]undecane,dilauryl phosphite,3,9-di[2,6-di-tert-butyl-4-methyl-phenoxy]-2,4,8,10-tetraoxa-3,9-diphosphaspiro[5.5]undecaneand tetrakis(2,4-di-tert-butylphenyl) 4,4′-bis(diphenylene)phosphonite,distearyl pentaerythritol diphosphite, diisodecyl pentaerythritoldiphosphite, 2,4,6-tri-tert-butylphenyl-2-butyl-2-ethyl-1,3-propanediolphosphite, tristearyl sorbitol triphosphite,tetrakis(2,4-di-tert-butylphenyl)4,4′-biphenylene diphosphonite,(2,4,6-tri-tert-butylphenyl)-2-butyl-2-ethyl-1,3-propanediolphosphite,tri-isodecylphosphite, octadecyl3,5-di-(tert)-butyl-4-hydroxyhydrocinnamate, and mixtures of phosphitescontaining at least one of the foregoing. Tris(2,4-di-tert-butylphenyl)phosphite, 2,4,6-tri-tert-butylphenyl-2-butyl-2-ethyl-1,3-propanediolphosphite, bis(2,4-di-tert-butylphenyl)pentaerythritol diphosphite, andbis(2,4-dicumylphenyl) pentaerythritol diphosphite are especiallypreferred, as well as mixtures of phosphites containing at least one ofthe foregoing phosphites, and the like.

[0040] Non-limiting examples of processing aids that can be used includeDoverlube® FL-599 (available from Dover Chemical Corporation),Polyoxyter® (available from Polychem Alloy Inc.), Glycolube P (availablefrom Lonza Chemical Company), pentaerythritol tetrastearate, MetablenA-3000 (available from Mitsubishi Rayon), neopentyl glycol dibenzoate,and the like.

[0041] The molding compositions of the present disclosure are preparedby mechanically blending the components in conventional mixingequipment, e.g., a single or twin-screw extruder, Banbury mixer, or anyother conventional melt compounding equipment. A vacuum may also beapplied to the equipment during the compounding operation to furtherreduce odorous materials emanating from the composition. The order inwhich the components of the composition are mixed is not generallycritical and may be readily determined by one of skill in this art.

[0042] The molding compositions described above are valuable forproducing a variety of useful articles. In an embodiment, the articlescomprise outdoor enclosures for electrical and telecommunicationsinterface devices, smart network interface devices, exterior andinterior vehicle parts, external housings for garden equipment, andexterior and interior building and construction parts. Non-limitingexamples of articles include those comprising exterior and interiorautomotive parts, window frames, window profiles, gutters, downspouts,siding, automotive bumper, doorliner, tailgate, interior parts, andfender; external housing for garden equipment, and snow scooter.

[0043] The molding compositions comprising different polymer resins andthe silicone-acrylate impact modifier compositions disclosed hereinposses superior properties, such as low temperature impact andductility, as compared to the polymer resin compositions which comprisesmethyl methacrylate-butadiene-styrene block copolymer impact modifier.

[0044] The previously described embodiments of the present inventionhave many advantages, including the ability to prepare thesilicone-acrylate impact modifier compositions, and new moldingcompositions having superior low temperature impact, ductility, and goodweatherability.

[0045] While only certain features of the invention have beenillustrated and described herein, many modifications and changes willoccur to those skilled in the art. It is, therefore, to be understoodthat the appended claims are intended to cover all such modificationsand changes as fall within the true spirit of the invention.

EXAMPLES

[0046] Notched Izod impact (hereinafter referred to as “NII”) wasmeasured by ISO 180 method, and expressed in kilojoules per meter square(kJ/m²). Ductility at a chosen temperature was measured using the impactenergy as well as stress whitening on the fracture surface. Generally,when stress whitening is observed, it indicates ductile failure mode.When stress whitening is not observed, it indicates a brittle failuremode. Ductility was measured by testing ten molded impact bars of aparticular composition at a given temperature. The percent ductility isexpressed as a percentage of impact bars that exhibited ductile failuremode.

[0047] Tensile strength was measured using ISO 527 method, and expressedin megapascals (Mpa). MVR was measured using ISO 1133 method (measuredat 260° C. using a 2.16 kilogram force), and are expressed in cubiccentimeres/10 minutes (cc/10 min). HDT was measured using ISO 179method, and are expressed in ° C. Flexural modulus (hereinafterdesignated as “FM”) was measured using ISO 178 method, and is expressedin gigapascals (Gpa).

[0048] The weatherability tests were carried out by using an Atlas G5000 accelerated weatherometer and ISO method SAE J1960. Test sampleswere exposed for about 1000 kilojoules to the xenon arc lamp in theweatherometer in accordance with the test method mentioned previously.The yellowness index (also called “YI”) values were measured using aGretag Mcbeth 7000A color spectrophotometer. The weatherability resultsare reported as yellowness index (also referred as “YI”) values. Glossmeasurements were carried out using Micro-TRI-Gloss instrument(available from BYK-Gardner, Germany). The gloss values are reported aspercent gloss retention (also referred to as “% GR”), which indicatesthe percent of the original gloss retained after the weatherabilitytest. The NI data was also measured at room temperature after theweatherability tests to determine the percent retention of notched Izodimpact at room temperature (also referred to as “% NIR”). A lower YI, ahigher % NIR retention, and a higher % GR retention would indicatebetter weatherabilihy performance.

[0049] The thermoplastic resins used were polycarbonate,styrene-acrylonitrile copolymer, and blends of PC and SAN, PC/PBT blends(available commercially as “Xenoy®” from GE Plastics), and ITR-PC(available commercially from GE Plastics as Sollx®). Table 1 shows theloading of the various ingredients in parts by weight for preparing themolding compositions. The impact modifiers used for forming the polymermolding compositions are: MBS (methyl methacrylate-butadiene-styrenecopolymer, commercially available from Rohm and Haas), S2001 (an impactmodifier commercially available from Mitsubishi Rayon), andsilicone-acrylate impact modifier compositions IM-1, IM-2, IM-3, IM-4,and IM-5, prepared using the general procedure described above.Comparative examples of molding compositions comprising IM-2, IM-5, MBS,and S2001 (a silicone acrylate impact modifier commercially availablefrom Mitsubishi Rayon Company) were also prepared. “PETS” stands forpentaerythritol tetrastearate. MZP stands for monozinc phosphate.

Example 1

[0050] This Example describes the general procedure for preparing IM-4silicone-acrylate impact modifier compositions by a semi-continuousemulsion polymerization process without a homogenization step.

[0051] A pre-emulsion mixture was prepared by combining D₄ (95.5 grams),tetraethylorthosilicate (2 grams), MPTMS (2.5 grams),dodecylbenzenesulfonic acid (0.5 grams), sodium dodecylbenzenesulfonate(1 gram), and deionized water (250 grams). About 20 percent by weight ofthe pre-emulsion mixture was charged together with deionized water (75grams) into a five-necked reactor equipped with a condenser, nitrogeninlet, and a stirrer, and the resulting mixture was stirred for about 3hours while maintaining the internal temperature at about 89° C. Theremainder of the pre-emulsion mixture was then fed continuously over a3-hour period with continued stirring. After being stirred for about 2hours at 89° C., the resulting latex was cooled down to roomtemperature. The pH of the silicone rubber latex was neutralized toabout 7-8 using 2-weight percent aqueous sodium hydroxide solution. Thefinal silicone rubber latex thus obtained had about 40 percent totalsolids, and corresponds to a silicone rubber monomer conversion of about89-91 percent.

[0052] The neutralized silicone rubber latex obtained above (70 grams)was mixed with deionized water (285 grams) and transferred to afour-necked round-bottomed flask equipped with a condenser, nitrogeninlet, and a mechanical stirring assembly. The contents of the reactorwas heated to about, 75° C. under a stream of nitrogen, followed byaddition of a solution of deionized water containing potassiumpersulfate (0.33 grains weight percent relative to combined weights ofisooctyl acrylate and triallyl cyanurate) and sodium bicarbonate (0.33grams weight percent relative to combined weights of isooctyl acrylateand triallyl cyanurate). Then the internal temperature was allowed toreach 75° C. To this mixture was added over a period of about 2 hours, amixture made up of isooctyl acrylate (29.4 grams) and triallyl cyanurate(0.6 grams). The polymerization reaction was allowed to continue foranother 2 hours at 75° C. to furnish the silicone-acrylate rubber latexhybrid. The monomer conversion is found to be about 96 percent.

[0053] The silicone-acrylate rubber latex hybrid obtained from theprevious step (75 grams) was introduced into a jacketed reaction flaskwith constant agitation, and heated to an internal temperature of about70° C. To this was added a solution made up of potassium persulfate(0.74 weight percent relative to combined weights of styrene and methylmethacrylate), sodium bicarbonate (0.74 weight percent relative tocombined weights of styrene and methyl methacrylate), and water (220grams). Then a pre-emulsion mixture of styrene (3.75 grams), methylmethacrylate (21.25 grams), sodium dodecylbenzenesulfonate (0.5 grams),and water (60 grams) was added to the reaction mixture, drop wise over a3-hour period, while maintaining the reactor internal temperature atabout 70° C. After the drop wise addition, the temperature of thereaction was maintained for another 2 hours at 70° C., and then cooledto room temperature. The monomer conversion in the resulting graftsilicone-acrylate rubber hybrid latex is around 97-98%.

[0054] The above graft silicone-acrylate rubber hybrid latex wascoagulated by first slowly adding one part by weight of the latex to 1.6parts by weight of an aqueous 0.5-0.75 weight percent calcium chloridesolution maintained at 70° C. with mechanical agitation, then continuingthe stirring for about 30 minutes, and then quenching the mixture byadding about 2 kilograms of water. The coagulated polymer product wasfiltered using a Buckner funnel, washed thoroughly with deionized waterat ambient temperature, and dried in air oven maintained at 70° C. forat least 24 hours.

[0055] The above-described method was used for preparing varioussilicone-acrylate modifiers, identified as TM-1, IM -2, IM -3, and IM-5.The monomers used for preparing each of the impact modifiers is shown inTable 1. “MMA” stands for methyl methacrylate. TABLE 1 Silicone Firstgraft Branched Second graft Polymerizable Impact rubber link acrylatelink alkenyl containing Modifier monomers monomer monomer(s) monomerorganic material IM-1 D⁴, TEOS MAPDMMS Isooctyl AllylStyrene/acrylonitrile acrylate methacrylate IM-2 D⁴, TEOS MAPDMMSn-butyl Allyl Styrene/acrylonitrile acrylate methacrylate IM-3 D⁴, TEOS,MPTMS Isooctyl Allyl Styrene/acrylonitrile acrylate methacrylate IM-4D⁴, TEOS, MPTMS Isooctyl TAC MMA/styrene acrylate IM-5 D⁴, TEOS, MPTMS2-ethylhexyl TAC MMA/styrene acrylate

Examples 2-5 and Comparative Examples 1-7

[0056] These examples describe molding composition formulations preparedusing various combinations of the thermoplastic resins and thesilicone-acrylate impact modifiers described previously. Theformulations prepared are shown in Table 1. In the table “NU” means theparticular ingredient was not used for making the formulation. Theseformulations were then used for preparing molding compositions asfollows.

[0057] The formulations described above were extruded into pellets usinga W&P ZSK25 twin-screw extruder and the conditions shown below. ZoneTemperature (Deg C.) Feed Hopper (Zone 1) 100 Zone 2 200 Zone 3 230 Zone4 240 Zone 5 (Nozzle) 250 Zone 6 260 Die 260

[0058] The pellets were injection molded into test specimens using anEngel 30-ton injection molder and the conditions shown below. ZoneTemperature (Deg C.) Feed Hopper (Zone 1)  70 Zone 2 230 Zone 3 245 Zone4 265 Zone 5 (Nozzle) 255 Mold 40-50

[0059] The properties were measured on the test specimens. Results areshown in Table 2. “NA” means data is not available.

[0060] Examination of the data shown in Example 2 of Table 2 indicatesthat the impact modifier prepared using isooctyl acrylate exhibits muchbetter percent ductility at temperatures equal to or lower than −20° C.,as compared with the corresponding molded part comprising MBS as theimpact modifier (Comparative Example 3), S2001 impact modifier(Comparative Example 2); and n-butyl acrylate impact modifier(Comparative Example 1). Furthermore, the MVR value for the PC-SAN basedmolding composition comprising isooctyl acrylate is much higher thanthat comprising MBS (Comparative Example 3), indicating that impactmodifiers prepared using isooctyl acrylate confer better processibilitywhen they are incorporated in molding compositions. A higher MVR isdesirable for better processibility. Moreover, PC-SAN based moldingcompositions retain the mechanical properties on par with those shown bymolding compositions comprising MBS.

[0061] PC-PBT based molding composition of Example 3, comprising theimpact modifier prepared using isooctyl acrylate as the branchedacrylate monomer shows better ductility at sub-zero temperatures whileretaining mechanical properties as compared to the composition ofComparative Example 4 (which comprises the impact modifier preparedusing 2-ethylhexyl acrylate) and Comparative Example 5 (using S2001impact modifier), but similar to that of Comparative Example 6 (usingMBS). Furthermore, the molding composition of Example 3 shows asignificantly better MVR of 9.9 as compared to a value of 6.3 shown bythe composition of Comparative Example 6. The molding composition ofExample 3 also displays superior weatherability, as shown by thesignificantly lower YI and % GR, and % NIR values, as compared to themolding composition of Comparative Example 6, which contains MBS impactmodifier.

[0062] The molding composition of Example 5 (comprising the isooctylacrylate-based impact modifier) shows superior ductility at or belowabout −20° C. below while retaining the mechanical properties, ascompared to the composition of Comparative Example 7 which showsductility only up to about −20° C.

[0063] While the disclosure has been illustrated and described intypical embodiments, it is not intended to be limited to the detailsshown, since various modifications and substitutions can be made withoutdeparting in any way from the spirit of the present disclosure. As such,further modifications and equivalents of the disclosure herein disclosedmay occur to persons skilled in the art using no more than routineexperimentation, and all such modifications and equivalents are believedto be within the spirit and scope of the disclosure as defined by thefollowing claims. All patents cited herein are incorporated herein byreference. TABLE 1 Parts by weight in each formulation ExampleIngredients used 2 1* 2* 3* 3 4 4* 5* 6* 7* 5 SAN 576 21.8 21.8 26.824.8 NU NU NU NU NU NU NU Phosphite  0.1  0.1  0.1  0.1  0.4  0.4  0.4 0.4  0.4 stabilizer-1 PETS  0.3  0.3  0.3  0.3 NU NU NU NU NU NU NUPhosphite  0.1  0.1  0.1  0.1 NU NU NU NU NU NU NU stabilizer-2 MZP NUNU NU NU  0.1  0.1  0.1  0.1  0.1 NU NU Phosphite NU NU NU NU NU NU NUNU NU  0.03  0.03 stabilizer-3 PC-105 40.4 40.4 44.4 44.4 46.4 46.4 46.446.4 46.4 NU NU PC-175 17 17 17 17 NU NU NU NU NU NU NU PBT-315 NU NU NUNU 12.9  9.4 12.9 13.9 12.9 NU NU PBT-195 NU NU NU NU 26.7 23.2 26.727.9 26.7 NU NU PET NU NU NU NU  0.3  0.3  0.3  0.3  0.3 NU NU Solix ®NU NU NU NU NU NU NU NU NU 86.7 80 IM-1 20 NU NU NU NU 20 NU NU NU NU NUIM-2 NU 20 NU NU NU NU NU NU NU NU NU IM-4 NU NU NU NU 13.3 NU NU NU NUNU NU IM-5 NU NU NU NU NU NU 13.3 NU NU NU NU IM-3 NU NU NU NU NU NU NUNU NU NU 20 S2001 NU NU 11.1 NU NU NU NU 11.11 NU NU NU ASA NU NU NU NUNU NU NU NU NU NU NU MBS NU NU NU 13.3 NU NU NU NU 13.3 13.3 NU

[0064] TABLE 2 Formu- NII (% ductility) lation at various temperaturesExample Ambient 0° C. −20° C. −30° C. −40° C. Tensile Flexural % 2 54(100) 52 51 45 44 43.5 8.4  98 2.24 NA NA NA 3 59 (100) 46 43 32 29 43.69.9  68 2.1 32.7 84 79 4 53 (100) 26 16 (0) NA 13 (0) 43.8 8.9  69.42.12 NA NA NA 5 65 (100) 57 51(100) 50 48 57 8.5 NA 2.19 NA NA NA 1*47(100) 41 38 29 (0) 28 (0) 44.6 6  99.7 2.18 NA NA NA 2* 52 (100) 47 20(0) 15 (0)  9 (0) 50.4 6.7 101 2.22 NA NA NA 3* 61 (100) 61 54 (60) 5241 (0) 45.7 1.9 103 2.24 NA NA NA 4* 55 (100) 50 35 (40) 21 (0) 16 (0)44.3 9.2 NA 2.2 NA NA NA 5* 56 (100) 47 21 (0) 21 (0) 16.5 36.9 16.6  731.88 NA NA NA 6** 53 (100) 50 50 46 42 41.7 6.3  71 2 41.1 69 72 7* 36(100) 34 30 26 22 (0) 57.6 3 NA 2.22 NA NA NA

1. A silicone-acrylate impact modifier composition, wherein said impactmodifier composition comprises structural units derived from: at leastone silicone rubber monomer, a branched acrylate rubber monomer havingthe formula:

wherein R¹ is selected from hydrogen and C₁-C₈ linear and branchedhydrocarbyl groups; and R² is a branched C₃-C₁₆ hydrocarbyl group; afirst graft link monomer, a polymerizable alkenyl-containing organicmaterial, and and a second graft link monomer.
 2. The impact modifiercomposition of claim 1, wherein R¹ is hydrogen and R² is at least onebranched hydrocarbyl radical selected from 4-methylpentyl,4-methylhexyl, and 5-methylhexyl.
 3. The impact modifier composition ofclaim 1, wherein said silicone rubber monomer comprises: at least onecyclic siloxane silicone rubber monomer of the formula:

wherein R³ and R⁴ are independently selected from hydrogen and C₁-C₁₀alkyl and aryl radicals; and “n” is an integer having a value from about3 to about 20; and at least one member selected from a trialkoxysilaneand tetraalkoxysilane of the general formula: (R⁵)_(s)Si(OR⁶)_(4-s);wherein R⁵ independently comprises hydrogen and C₁-C₁₀ alkyl and arylradicals; R⁶ independently comprises C₁-C₄ hydrocarbyl radicals; and “s”is an integer having a value from about 0 to about
 1. 4. The impactmodifier composition of claim 1, wherein said silicone rubber monomercomprises: at least one member selected fromoctamethylcyclotetrasiloxane, decamethylcyclopentasiloxane, andhexamethylcyclotrisiloxane; and tetraethoxysilane.
 5. The impactmodifier composition of claim 1, wherein said polymerizable alkenylcontaining organic material comprises at least one aromatic vinylmonomer, olefinic nitrile; and branched and unbranched (meth)acrylatemonomer.
 6. The impact modifier composition of claim 1, wherein saidpolymerizable alkenyl containing organic material is at least oneselected from the group consisting of styrene, alpha-methylstyrene,acrylonitrile, methacrylonitrile, butyl acrylate, and methylmethacrylate.
 7. The impact modifier composition of claim 1, whereinsaid first graft link monomer comprises at least one of an(acryloxy)alkoxysilane, a (mercaptoalkyl)alkoxysilane, avinylalkoxysilane, and an allylalkoxysilane.
 8. The impact modifiercomposition of claim 1, wherein said first graft link monomer comprisesat least one of (gamma-methacryloxypropyl)(dimethoxy)methylsilane,(3-mercaptopropyl)alkoxysilane, vinyltrimethoxysilane, andallyltrimethoxysilane.
 9. The impact modifier composition of claim 1,wherein said second graft link monomer is at least onepolyethylenically, unsaturated compound having at least one allyl group.10. The impact modifier composition of claim 1, wherein said secondgraft link monomer is at least one selected from the group consisting ofallyl methacrylate, triallyl cyanurate, triallyl isocyanurate, anddiallylmaleate.
 11. A silicone-acrylate impact modifier composition,wherein said composition comprises structural units derived from: asilicone rubber monomer comprising octamethylcyclotetrasiloxane andtetraethoxysilane; a branched acrylate rubber monomer selected from thegroup consisting of iso-octyl acrylate, 6-methyloctyl acrylate,7-methyloctyl acrylate, and combinations of the foregoing branchedacrylate rubber monomers; at least one first graft link monomer selectedfrom the group consisting of(gamma-methacryloxypropyl)(dimethoxy)methylsilane and(3-mercaptopropyl)trimethoxysilane; a polymerizable alkenyl-containingorganic material comprising at least one of styrene,alpha-methylstyrene, acrylonitrile, methacrylonitrile, methylmethacrylate; and at least one second graft link monomer selected fromthe group consisting of all methacrylate, triallyl cyanurate, andtriallyl isocyanurate.
 12. The impact modifier composition of claim 11,wherein said impact modifier composition further comprises structuralunits derived from at least one acrylate monomer selected from the groupconsisting of linear alkyl acrylates.
 13. A molding compositioncomprising a polymer resin and a silicone-acrylate impact modifiercomposition, wherein said impact modifier composition comprisesstructural units derived from: at least one silicone rubber monomer, abranched acrylate rubber monomer having the formula:

wherein R¹ is selected from hydrogen and C₁-C₈ linear and branchedhydrocarbyl groups; and R² is a branched C₃-C₁₆ hydrocarbyl group; afirst graft link monomer, a polymerizable alkenyl containing organicmaterial, and and a second graft link monomer; wherein said moldingcomposition has ductile-to-brittle transition temperature from about 0°C. to about −60° C.
 14. The molding composition of claim 13, whereinsaid polymer is selected from thermoplastic and thermoset polymers. 15.The molding composition of claim 14, wherein said thermoplastic polymeris selected from the group consisting of polycarbonates, polyesters,polyolefins, polyestercarbonates, polyamides, polyethersulfones,polyetherimides, polyphenylenes ether, acrylate polymers, styrenicpolymers, vinyl halide polymers, and blends of the foregoing polymers.16. The molding composition of claim 14, wherein said thermoplasticpolymer is bisphenol A polycarbonate,1,3-bis(4-hydroxyphenyl)-1-methyl-4-isopropylcyclohexane polycarbonate,polybutylene terephthalate, polyethylene terephthalate,acrylonitrile-styrene-acrylate core shell polymers,acrylonitrile-styrene-alpha-methylstyrene-acrylate core shell polymers,styrene-acrylonitrile copolymer, styrene-methacrylonitrile copolymer,acrylonitrile-butadiene-styrene copolymer,acrylonitrile-alpha-methylstyrene-butadiene copolymer, copolymerscomprising structural units derived from isophthalic acid, terephthalicacid, resorcinol, and bisphenol A; and blends of the foregoing polymers.17. The molding composition of claim 13, wherein said impact modifiercomposition further comprises structural units derived from at least oneacrylate monomer selected from the group consisting of linear alkylacrylates.
 18. An article of manufacture comprising the impact modifiercomposition of claim
 1. 19. The article of claim 18, wherein saidarticle comprises outdoor enclosures for electrical andtelecommunications interface devices, smart network interface devices,exterior and interior vehicle parts, external housings for gardenequipment, and exterior and interior building and construction parts.20. The article of claim 18, wherein said article comprises exterior andinterior automotive parts, window frames, window profiles, gutters,downspouts, siding, automotive bumper, doorliner, tailgate, interiorparts, and fender; external housing for garden equipment, and snowscooter.
 21. A molding composition comprising a polymer resin and asilicone-acrylate impact modifier composition, wherein impact modifiercomposition comprises structural units derived from: a silicone rubbermonomer comprising octamethylcyclotetrasiloxane and tetraethoxysilane; abranched acrylate rubber monomer selected from the group consisting ofiso-octyl acrylate, 6-methyloctyl, 7-methyloctyl, and combinations ofthe foregoing branched acrylate rubber monomers; at least one firstgraft link monomer selected from the group consisting of(gamma-methacryloxypropyl)(dimethoxy)methylsilane and(3-mercaptopropyl)trimethoxysilane; a polymerizable alkenyl-containingorganic material comprising at least one of styrene,alpha-methylstyrene, acrylonitrile, methacrylonitrile, methylmethacrylate; and at least one second graft link monomer selected fromthe group consisting of allyl methacrylate and triallylcyanurate;wherein said molding composition has ductile-to-brittle transitiontemperature from about 0° C. to about −60° C.
 22. The moldingcomposition of claim 21, wherein said impact modifier compositionfurther comprises structural units derived from at least one acrylatemonomer selected from the group consisting of linear alkyl acrylates.23. A method for making a silicone-acrylate impact modifier composition,said method comprising: emulsion polymerizing at least one siliconerubber monomer and a first graft link monomer at a temperature fromabout 30° C. to about 110° C. to form a silicone rubber latex; adding tosaid silicone rubber latex, at a pH of about 4 to about 9.5, and atemperature of about 20° C. to about 90° C., at least one branchedacrylate rubber monomer and a second graft link monomer to provide alatex comprising an emulsion polymerized silicone-acrylate rubberhybrid; grafting said silicone-acrylate rubber hybrid with apolymerizable alkenyl containing organic material to form a graftsilicone-acrylate rubber hybrid latex; and, coagulating, washing, anddrying said graft silicone-acrylate rubber hybrid latex to provide saidsilicone-acrylate rubber impact modifier composition; wherein said atleast one branched acrylate rubber monomer has the formula:

wherein R¹ is selected from hydrogen and C₁-C₈ linear and branchedhydrocarbyl groups; R² is a branched C₃-C₁₆ hydrocarbyl group.
 24. Themethod of claim 23, wherein said method further comprises adding to saidsilicone rubber latex, at least one acrylate monomer selected from thegroup consisting of linear alkyl acrylates.
 25. The method of claim 23,wherein said silicone rubber latex has a volume average particle sizefrom about 100 nanometers to about 2 microns.
 26. The method of claim23, wherein said polymerizable alkenyl containing organic material is atleast one selected from the group consisting of styrene,alpha-methylstyrene, acrylonitrile, methacrylonitrile, and methylmethacrylate.